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Quote:

Originally Posted by Lonewolf_50

I got the idea that with no (or very little) thrust, and with the aircraft falling, the pilot (may have) realized that he was in out of control flight , and falling.
In a pedantic sense: if you make control inputs, and the aircraft won't or can't respond to them, you are in out of control flight .

That doesn't seem to be contradicted by the only data we have - computed bearings, allowing for GPS error margins don't show any lateral course change after rotation.

computed bearings from ADS-B positions

Given the ADS-B height figures are reported to have a granularity of 25' it's compatible with the video to assume a height around 90' at the last ADS-B data point. A simple ballistic calculation - speed 88m/s (171kt), 11degrees, 30m height, results in a maximum height of 145' - given the impact of aerodynamics the observed height in the video isn't in dramatic disagreement - ie it's possible nothing interrupted the flight path after rotation.

Given the clearer land 100' to the left of the flight line the "in out of controlled flight" is sadly very feasible.

Subjects ADSB

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Quote:

Originally Posted by MaybeItIs

There are safer batteries that are not lead-acid whales. Are the any other planes out there that need fireproof boxes and vent pipes to contain and purge burning battery fumes etc to the outside ?

[my emphasis]

To put this to rest as well - here is the Lithium battery thermal protection for what is arguably the most modern (non-Boeing) airliner out there: the Airbus A350 series.



Source: https://aircraft.airbus.com/sites/g/...irefighter.pdf

Subjects: None

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Quote:

Originally Posted by Kraftstoffvondesibel

This has also been touched upon earlier in the thread, but it rather seems the cut-off switches are in the same LRU, in close proximity, using the same connector and goes through the same wiring harness. No one was able to say whether it works purely by digital signaling, and goes through any common software, or if it is duplicated by purely direct signaling. There might be numerous failure modes of the cut-off switch design, it is obviously very, very robust and overall sound, since dual failures here have never happened, but this is alredy an outlier event.

If we are to take the TCMA patent at face value, the fuel cut-off switches are directly-acting, not some sort of signalling protocol.

That's a pretty big "if" but here's the patent drawing:

Subjects Fuel (All)  Fuel Cutoff  Fuel Cutoff Switches

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This is my latest attempt to square the circle using all the data points and minimal assumptions. The main shortcoming of the analysis is not knowing the maximum L/D and the speed for maximum LD with the gear down, flaps 5, and the RAT extended. However, if I use a reasonable number in my opinion for the L/D in that configuration and assume that the airplane is being flown at the speed for it, it will not get to the crash site. The distance from the runway of the crash site is from a previous graphic (1.55 km); the rotation point from fdr, permalink 314; 200 feet max height above the runway being generally accepted; crash site 50 feet below the runway elevation cited previously. An average speed of 180 knots is consistent with the dimensions given and 30 seconds flight time. A flare at 50 feet will briefly increase the L/D to 20, maybe even 30 (500 feet more than shown) but still not enough to make up the shortfall, In fact, with a head wind the L/D will be lower than assumed as well as if the speed being flown is higher or lower than required for maximum L/D in that configuration. In other words, there must have been some thrust available.

Subjects RAT (All)  RAT (Deployment)

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Quote:

Both engines run from the center tank on takeoff if it has fuel in the tank which was the case on this flight

I'm afraid not, take off and landing are considered high risk as far as fuel supply is concerned and the following FAR is relevant,

\xa7 25.953 Fuel system independence.

Each fuel system must meet the requirements of \xa7 25.903(b) ( (b) Engine isolation. The powerplants must be arranged and isolated from each other to allow operation, in at least one configuration, so that the failure or malfunction of any engine, or of any system that can affect the engine, will not— (1) Prevent the continued safe operation of the remaining engines; or

(2) Require immediate action by any crewmember for continued safe operation )

by—

(a) Allowing the supply of fuel to each engine through a system independent of each part of the system supplying fuel to any other engine; or

(b) Any other acceptable method

That is, during these periods each engine must be supplied with fuel from a separate tank, you don't want all engines being supplied by the same tank and run the risk of losing all engines due to contamination in that one tank.

Switch over to the centre tank to feed all engines typically takes place at 10,000'

Subjects Centre Tank  Fuel (All)

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Quote:

Originally Posted by Megan

Switch over to the centre tank to feed all engines typically takes place at 10,000'

Hold your horses, Megan, that doesn't mean you do it at 10,000, only that IF the message shows, turn them on. Here's part of the Before Start procedure (very early FCOM):

Subjects Centre Tank  FCOM

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Quote:

Originally Posted by Tailspin Turtle

This is my latest attempt to square the circle using all the data points and minimal assumptions. The main shortcoming of the analysis is not knowing the maximum L/D and the speed for maximum LD with the gear down, flaps 5, and the RAT extended. However, if I use a reasonable number in my opinion for the L/D in that configuration and assume that the airplane is being flown at the speed for it, it will not get to the crash site. The distance from the runway of the crash site is from a previous graphic (1.55 km); the rotation point from fdr, permalink 314; 200 feet max height above the runway being generally accepted; crash site 50 feet below the runway elevation cited previously. An average speed of 180 knots is consistent with the dimensions given and 30 seconds flight time. A flare at 50 feet will briefly increase the L/D to 20, maybe even 30 (500 feet more than shown) but still not enough to make up the shortfall, In fact, with a head wind the L/D will be lower than assumed as well as if the speed being flown is higher or lower than required for maximum L/D in that configuration. In other words, there must have been some thrust available.

Two points:

1) I had seen the "50 feet below runway" referenced as well, and double-checked on Google Earth, and could not confirm this. The terrain looks reasonably level. I'd be happy to see evidence for this claim, but until I do, I'll think it's false.

2) The maximum L/D is given for optimal speed, which remains constant throughout the glide. In the AI171 case, drag is balanced not just by loss of altitude (as it is in the optimal glide), but also by loss of speed. The speed decline provides energy, and I suspect that makes up the shortfall you assign to thrust.

Note that kinetic energy is proportional to v\xb2, i.e. a speed loss of 50 knots from 180 to 130 vs 50 to 0 provides 15500 vs 2500 units of energy, i.e. 6 times as much. If you hypothetically hurl a unpowered aircraft into the sky with a catapult (and if there was no drag), hurling it at 180 knots makes it go 6 times as high by the time its speed decays to 130 knots than it could ever go if you hurled it at 50 knots. Of course there's drag in reality, and that also varies with v\xb2, so this is a very theoretical consideration intended to calibrate your expectations.

I remember that someone used some kind of tool to confirm that the aircraft could've gone unpowered for as long as we assume it did, but of course I can't find it again now. :-(

Subjects AI171  RAT (All)  RAT (Deployment)

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Quote:

Originally Posted by megan

Hold your horses there Bloggs , I didn't say they did, I said centre tanks were typically turned on at that altitude (using a certain 737 operator as a guide). As the check list that you posted shows the centre pumps will automatically turn off because of load shedding once an engine is started.

I have an up to date B787-9 FCOM and it agrees with Bloggs. Centre tank pumps are switched on prior to start. Load shedding is just until all electrics are available, ie until after engine start, then the centre tank pumps are operational as far as I can tell.

Subjects Centre Tank  FCOM

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Quote:

Originally Posted by Tailspin Turtle

This is my latest attempt to square the circle using all the data points and minimal assumptions. The main shortcoming of the analysis is not knowing the maximum L/D and the speed for maximum LD with the gear down, flaps 5, and the RAT extended. However, if I use a reasonable number in my opinion for the L/D in that configuration and assume that the airplane is being flown at the speed for it, it will not get to the crash site. The distance from the runway of the crash site is from a previous graphic (1.55 km); the rotation point from fdr, permalink 314; 200 feet max height above the runway being generally accepted; crash site 50 feet below the runway elevation cited previously. An average speed of 180 knots is consistent with the dimensions given and 30 seconds flight time. A flare at 50 feet will briefly increase the L/D to 20, maybe even 30 (500 feet more than shown) but still not enough to make up the shortfall, In fact, with a head wind the L/D will be lower than assumed as well as if the speed being flown is higher or lower than required for maximum L/D in that configuration. In other words, there must have been some thrust available.

There is easily-correctable available data with the aircraft's altitude at pretty much the end of the runway and it is not at 200 feet (it's around 100\xb112.5 feet).

As the aircraft visibly continues to climb past that height (and for a longer period than ADS-B data covers, if the camera's perspective casts doubt on that), it seems rather clear to me that it reached its peak height past the end of the runway.

In light of this I find the fact that people keep calculating a glide from the runway to the crash site to be a bit strange. Wouldn't the first step of any math be to try to determine where it started descending?

Subjects ADSB  RAT (All)  RAT (Deployment)

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Quote:

Originally Posted by AerocatS2A

I have an up to date B787-9 FCOM and it agrees with Bloggs. Centre tank pumps are switched on prior to start. Load shedding is just until all electrics are available, ie until after engine start, then the centre tank pumps are operational as far as I can tell.

It's exactly the same on the B777 - the centre fuel pump switches go on before start if the FUEL IN CENTER EICAS message is displayed. The switches go off again when the FUEL LOW CENTER message is displayed. On the ground, the B777 needs two power sources for both centre tank pumps to operate, so one pump is normally shed until after engine start. The centre tank pumps output about three times the pressure of the main tank pumps. Fuel is fed from the centre tank until the centre tank pumps are selected off.

Subjects Centre Tank  EICAS  FCOM  Fuel (All)

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There has been discussion recently about a procedure that involves moving the fuel switches to CUTOFF and then back to RUN following a dual engine failure.

Attached is an image of a page from the Air India 787 Training Manual that discusses this procedure.

I am submitting this without comment or opinion.

Subjects Dual Engine Failure  Engine Failure (All)  Fuel (All)  Fuel Cutoff Switches  RUN/CUTOFF

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For info only - re-post of lever-lock fuel-switch design:




B787 Fuel Control Switches -

---

Last edited by PJ2; 9th July 2025 at 17:45 . Reason: Add image of B787 Fuel Control Switches

Subjects Fuel (All)  Fuel Cutoff Switches

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Quote:

Originally Posted by PJ2

For info only - re-post of lever-lock fuel-switch design:




B787 Fuel Control Switches -

A bit of a pedantic point, but the locking lever in the photo above is not the right action for the fuel cut off switches on the 787. The switch above has two locked positions and a biased further position. You could say ON-OFF-BIASSED. There are some photos earlier in the thread (assuming they are still there) of the correct Honeywell switch and its gate.

Edit: And here it is:

Subjects Fuel (All)  Fuel Cutoff  Fuel Cutoff Switches  Honeywell

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Quote:

Originally Posted by V1... Ooops

There has been discussion recently about a procedure that involves moving the fuel switches to CUTOFF and then back to RUN following a dual engine failure.

Attached is an image of a page from the Air India 787 Training Manual that discusses this procedure.

I am submitting this without comment or opinion.

Nobody seems to have discussed this. If I'm reading it right (and I'm not a pilot), it seems to be suggesting that in the event of a dual engine failure, a restart should be attempted while the engine still has high RPM? It also seems to be indicating that fuel switch resetting should be attempted if the restart has failed to start the engine?

Subjects Dual Engine Failure  Engine Failure (All)  Fuel (All)  Fuel Cutoff Switches  RUN/CUTOFF  Relight  V1

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Quote:

Originally Posted by AirScotia

Nobody seems to have discussed this. If I'm reading it right (and I'm not a pilot), it seems to be suggesting that in the event of a dual engine failure, a restart should be attempted while the engine still has high RPM?

That's how I read this:


Obviously, because it's going to require quick action to catch high RPM. And maybe that's what they tried.

Quote:

It also seems to be indicating that fuel switch resetting should be attempted if the restart has failed to start the engine?

Not sure about this. I think it's saying Resetting to initiate a Restart attempt. Not repeating it.

Subjects Dual Engine Failure  Engine Failure (All)  Fuel (All)  Fuel Cutoff Switches  Relight

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Quote:

Originally Posted by cLeArIcE

It is not inconceivable to me that a human being who THINKS they've had a dual engine failure at possibly the worst time imaginable (correctly or incorrectly) and has not taken the time to confirm, or take it all in and has immediately launched into memory items. I could certainly foresee one being rather startled by the energy state and the rapidly approaching buildings.
I'm not saying that this happened to this crew but it certainly could happen to someone. People do weird !!!! under high stress. There is an initial "oh !!!!, what's going on" then the training kicks in. Often at super fast rate and the challenge becomes slowing it all down.
The bloody master warning on the Airbus for smoke in the forward Lav used to get me everytime. Was always at night over the ocean too.

It\x92s also not inconceivable that a human being who KNOWS they\x92ve had a dual engine failure at the worst time has immediately launched into memory items. Those memory items include \x91cycling\x92 the fuel cut off switches\x85

Subjects Dual Engine Failure  Engine Failure (All)  Fuel (All)  Fuel Cutoff  Fuel Cutoff Switches  Memory Items

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Quote:

Originally Posted by sixgee

Ex 787 pilot here, I can confirm that the excerpt from the FCTM above is correct, and also confirm that the QRH memory items for Dual Engine Fail/Stall are:

Condition: Engine speed for both engines is below idle

Fuel Control Switches (both) \x85 CUTOFF then RUN
RAM AIR TURBINE switch \x85 Push and hold for1 second

Here ya go

Subjects Fuel (All)  Fuel Cutoff Switches  Memory Items  RUN/CUTOFF

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Quote:

Originally Posted by moosepileit

787 pilots, If throttles are NOT at idle, will their respective fuel cut off switches still trigger a shutdown?

The above checklist procedure implies throttle lever angle and cutoff switches are independant for resetting FADECs.

If so, is it time for this convention from the days where throttles and cutoffs were mechanical systems, not resolvers and switches, to end?

Risk vs reward? Requires more coordination between PF and PM in cases where cutoff is not desired by PF- keep throttle/s up, cannot be surprised by a fuel cutoff.

Yes, switch directly controls spar valve (fuel supply) position - no fuel - no fire.

Subjects Fuel (All)  Fuel Cutoff  Fuel Cutoff Switches  Spar Valves

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Quote:

Originally Posted by galaxy flyer

Just for emphasis, the fuel control switches control both the spar valve AND the shutoff inside the fuel controller at the engine. It\x92s not the spar valve the starves the engine of fuel it\x92s the HP valve. If it were only the spar valve, shut downs at the gate would take awhile.

Not entirely correct, the engine fuel valve is controlled by fire handle, the spar valves are at the tank. See attached.

Subjects Fuel (All)  Fuel Cutoff Switches  Spar Valves

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This part of the report shows how early the RAT was out.

Subjects RAT (All)

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